A crucial outcome measurement of surgical treatments of atrial fibrillation (AF) such as the Maze and Radial procedures is the preservation of normal atrial function. However, knowledge of normal and abnormal atrial function is sparse, and the techniques to accurately characterize atrial function and its complex three-dimensional nature are limited. This lack of a reliable method to characterize atrial function has limited both experimental and clinical evaluation of the physiological consequences of the surgical treatment of AF. Recently, cardiac magnetic resonance imaging (CMR) has for the first time allowed for the accurate quantification of atrial function. Previous studies have demonstrated reduced atrial function with the Maze procedure and greater preservation of atrial function with the Radial procedure to ablate AF. However, cardiac echocardiography was used to make these assessments. There have been no studies on the effect of the multiple incisions of these procedures on regional wall motion or overall atrial ejection due to limitations of echocardiography. With CMR, the physiological and functional consequences of surgical treatment will be examined. This will allow the development of less invasive surgical techniques to treat AF.